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A sorus (pl.: sori) is a cluster of sporangia (structures producing and containing spores) in ferns and fungi. A coenosorus ( pl. : coenosori ) is a compound sorus composed of multiple, fused sori. Etymology
Fern fronds often bear sporangia, where the plant's spores are formed, usually on the underside (abaxial surface) of the pinnae, but sometimes marginally or scattered over the frond. The sporangia are typically clustered into a sorus (pl., sori). Associated with each sorus in many species is a membranous protective structure called an indusium ...
Millions of spores are released at harvest and contaminate healthy kernels or land on other plant parts or the soil. The spores persist on the contaminated kernels or in the soil. The disease is initiated when soil-borne, or in particular seed-borne, teliospores germinate in response to moisture and produce hyphae that infect germinating seeds ...
The mature sporangia have a wall that is just a single cell thick, [8] and are typically covered with a scale called the indusium, which can cover the whole sorus, forming a ring or cup around the sorus, or can also be strongly reduced to completely absent. Many leptosporangiate ferns have an annulus around the sporangium, which ejects the ...
There are around 64 spores in a leptosporangium. Scanning electron micrograph of fern leptosporangia. In a eusporangium, characteristic of all other vascular plants and some primitive ferns, the initials are in a layer (i.e., more than one). A eusporangium is larger (hence contain more spores), and its wall is multi-layered.
The false indusia look similar, though not identical, to the rest of the leaf tissue, and are 0.05–0.25 mm wide. Beneath them, the sori do not form long lines, but are discontinuous and concentrated on lobes at the tip and sides of the pinnule. Each sporangium in a sorus carries 64 spores. The diploid sporophyte has a chromosome number of 60.
In the Salviniaceae family, the sporocarp is nothing more than a modified sorus, a single cluster of spore-producing tissues enclosed by a thin sphere of tissue and attached to the leaves. In the Marsileaceae (water-clover) family, the sporocarp is a more elaborate structure formed from an entire leaf whose development and form is greatly modified.
The resilient nature of the resting spores, the overwintering sporangia, is the principal challenge in managing the disease. Several means of control have been explored, including chemical [9] [10] and biological, [11] but have been largely ineffective, impractical, or neglected. Cultivation of resistant varieties is the best management approach.